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Abstract

Gravitational wave observations can provide unprecedented insight into the
fundamental nature of gravity and allow for novel tests of modifications to
General Relativity. One proposed modification suggests that gravity may undergo
a phase transition in the strong-field regime; the detection of such a new
phase would comprise a smoking-gun for corrections to General Relativity at the
classical level. Several classes of modified gravity predict the existence of
such a transition - known as spontaneous scalarization - associated with the
spontaneous symmetry breaking of a scalar field near a compact object. Using a
strong-field-agnostic effective-field-theory approach, we show that all
theories that exhibit spontaneous scalarization can also manifest dynamical
scalarization, a phase transition associated with symmetry breaking in a binary
system. We derive an effective point-particle action that provides a simple
parametrization describing both phenomena, which establishes a foundation for
theory-agnostic searches for scalarization in gravitational-wave observations.
This parametrization can be mapped onto any theory in which scalarization
occurs; we demonstrate this point explicitly for binary black holes with a toy
model of modified electrodynamics.